Testing email services in SpringBoot - spring

Question

I've generated a Spring Boot web application using Spring Initializer, embedded Tomcat, Thymeleaf template engine, and package as an executable JAR file.
Technologies used:
Spring Boot 1.4.2.RELEASE, Spring 4.3.4.RELEASE, Thymeleaf 2.1.5.RELEASE, Tomcat Embed 8.5.6, Maven 3, Java 8
I have this email service that I want to test
#Service
public class MailClient {
protected static final Logger looger = LoggerFactory.getLogger(MailClient.class);
#Autowired
private JavaMailSender mailSender;
private MailContentBuilder mailContentBuilder;
#Autowired
public MailClient(JavaMailSender mailSender, MailContentBuilder mailContentBuilder) {
this.mailSender = mailSender;
this.mailContentBuilder = mailContentBuilder;
}
//TODO: in a properties
public void prepareAndSend(String recipient, String message) {
MimeMessagePreparator messagePreparator = mimeMessage -> {
MimeMessageHelper messageHelper = new MimeMessageHelper(mimeMessage);
messageHelper.setFrom("nunito#calzada.com");
messageHelper.setTo(recipient);
messageHelper.setSubject("Sample mail subject");
String content = mailContentBuilder.build(message);
messageHelper.setText(content, true);
};
try {
if (looger.isDebugEnabled()) {
looger.debug("sending email to " + recipient);
}
mailSender.send(messagePreparator);
} catch (MailException e) {
looger.error(e.getMessage());
}
}
}
I've created this test class
#RunWith(SpringRunner.class)
public class MailClientTest {
#Autowired
private MailClient mailClient;
private GreenMail smtpServer;
#Before
public void setUp() throws Exception {
smtpServer = new GreenMail(new ServerSetup(25, null, "smtp"));
smtpServer.start();
}
#Test
public void shouldSendMail() throws Exception {
//given
String recipient = "nunito.calzada#gmail.com";
String message = "Test message content";
//when
mailClient.prepareAndSend(recipient, message);
//then
String content = "<span>" + message + "</span>";
assertReceivedMessageContains(content);
}
private void assertReceivedMessageContains(String expected) throws IOException, MessagingException {
MimeMessage[] receivedMessages = smtpServer.getReceivedMessages();
assertEquals(1, receivedMessages.length);
String content = (String) receivedMessages[0].getContent();
System.out.println(content);
assertTrue(content.contains(expected));
}
#After
public void tearDown() throws Exception {
smtpServer.stop();
}
}
But I got this error when running the test
Error creating bean with name 'com.tdk.service.MailClientTest': Unsatisfied dependency expressed through field 'mailClient'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.tdk.service.MailClient' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {#org.springframework.beans.factory.annotation.Autowired(required=true)}

Answer 1

The problem is that you want to run an integration test without providing the beans!
Whenever you use #Autowired, you need to provide the beans required for the autowired component feed via context.
Therefore, you need to add a static class inside that test class with #Configuration annotation. Moreover, the test class also need to know which configuration must be used via #ContextConfiguration annotation. An example here:
#RunWith(SpringRunner.class)
#ContextConfiguration(classes = {MailClientTest.ContextConfiguration.class})
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class MailClientTest {
#Configuration
#TestPropertySource(locations = "classpath:application.properties",
properties ={"my.additiona.property=123"})
#ComponentScan(basePackages = {"com.tdk.service"})
public static class ContextConfiguration {
#Bean
public JavaMailSender mailSender{
return ... //create the instance here
}
#Bean
public MailContentBuilder mailContentBuilder() {
return ... //create the instance here
}
}
}
Anyway, as I already pointed out in a comment, don't waste your time reinventing the wheel. There is already a library out of there that does all this stuff for you. I'm talking about Spring Boot Email Tools.
I think it is worth to use that library and maybe contribute to the repository with new features instead of spending time for reimplementing email support with template engines.